This internal NSA technical newsletter states that the source of information codenamed MONEYROCKET is collecting information on “senders and receivers of bitcoin” and users Liberty Reserve: see the Intercept article The NSA Worked To “track Down” Bitcoin Users, Snowden Documents Reveal, 20 March 2018.

This NSA classification guide, dated 21 November 2011, covers signals intelligence material that as to be kept secret for more than the standard 60 years: see the Der Spiegel article The NSA in Germany: Snowden’s Documents Available for Download, 18 June 2014.